Scientists Partially Reconstruct Genome of Extinct Mammoth

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Elephants evolved in a tropical habitat, and the species surviving today live only in very warm places. Their chief problem is dispersing the heat generated by their massive bodies. Woolly mammoths apparently moved into the Arctic about 2 million years ago. Their chief problem was conserving body heat, exactly the opposite.

How mammoths were able to adapt through natural selection to such different conditions -- while remaining 99.4 percent identical to elephants -- is a matter of intense interest to evolutionary biologists.

"It was relatively rapid shift, a relatively recent shift and a dramatic change," said Michael Hofreiter, a molecular geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Mammoths are among the few mammals that re-evolved the ability to grow thick hair, a capacity their ancestors had lost. They had other heat-saving features, such as small ears and short tails. But the most interesting changes almost certainly involve metabolism, use and storage of fat, and circulation.

"That's what we really want to learn -- what made a mammoth a mammoth," Poinar said.

Curiously, there is evidence that natural selection may ultimately have failed at least one limb of the woolly mammoth family tree.

Schuster and his colleagues determined that the 65,000-year-old animal was from a subspecies that died out about 45,000 years ago. That was before there were human beings in Siberia to hunt it.

"You have to ask: How can a species that made it through so many ice ages suddenly go extinct?" Schuster said. "It seemed that the genetic outfit of that mammoth did not have enough 'plasticity' anymore for it to deal with challenges coming from the environment."

As for bringing mammoths back to life, that is still firmly the domain of science fiction. It would require retrofitting an elephant cell with hundreds of thousands of mammoth-making mutations or building the nucleus of a mammoth cell from scratch -- both impossible at the moment.

J. Craig Venter, one of the sequencers of the human genome, has synthesized from chemical compounds the genes of a bacterium, Mycoplasma genitalium.

"We have not yet booted it up," he said yesterday, referring to the next step of putting the manmade genes into a bacterium whose native genes have been removed to see whether the whole thing will grow and divide.